Switching power converters are widely used in modern electronic systems for a variety of applications such as computing (server and mobile) and POLs (Point-of-Load Systems) for telecommunications because of their high efficiency and small amount of area/volume consumed by such converters. Widely accepted switching power converters include buck, boost, buck-boost, forward, flyback, half-bridge, full-bridge, and SEPIC topologies. Multiphase buck converters are particularly well suited for providing high current at low voltages needed by high-performance integrated circuits such as microprocessors, graphics processors, and network processors. Buck converters are implemented with active components such as a pulse width modulation (PWM) controller IC (integrated circuit), driver circuitry, one or more phases including power MOSFETs (metal-oxide-semiconductor field-effect transistors), and passive components such as inductors, transformers or coupled inductors, capacitors, and resistors. Multiple phases can be connected in parallel to the load through respective inductors to meet high output current requirements.
Modern and high performance power supplies need phase current information to provide the load with high quality power. Phase current information is critical in providing key features such as phase fault detection, current balancing, power saving modes, over current and negative current protection, and improved transient response. Conventional multi-phase digital switching power converters include current sense/sampling networks for obtaining phase current information. However conventional current sampling networks consume a lot of power and area on the controller chip (die), thus creating a need for a high performance current sampling network with low power and area consumption.
For example, one conventional approach for sampling phase current information is a high resolution and high speed current flash ADC (analog-to-digital converter). Flash ADCs provide fast conversion and high precision, but are high cost and high leakage current, high power and area consumption on the controller chip. Another conventional approach for obtaining phase current information is a tracking ADC. However, tracking ADCs are susceptible to noise, have relatively high power and area consumption on the controller chip and have poor tracking capability and performance at high switching frequencies. Still another conventional approach for obtaining phase current information is a Sigma-Delta ADC. However, Sigma-Delta ADCs have poor tracking capability at high switching frequencies, require over-sampling at a rate much larger than the signal bandwidth, and have significant latency between the digital outputs and corresponding sampling instants.